Method and apparatus for identifying scale invariant features in an image and use of same for locating an object in an image
First Claim
1. A method of identifying scale invariant features in an image defined by a plurality of pixels, the method comprising:
- locating pixel amplitude extrema in a plurality of difference images produced from said image by;
comparing the amplitude of each pixel in an image under consideration with the amplitudes of pixels in an area about said each pixel in said image under consideration to identify local maximal and minimal amplitude pixels;
comparing the amplitudes of said local maximal and minimal amplitude pixels with the amplitudes of pixels in a predecessor image to the image under consideration to identify possible maximal and minimal amplitude pixels and comparing the amplitudes of said possible maximal and minimal amplitude pixels with the amplitudes of pixels in a successor image to the image under consideration to identify actual maximal and minimal amplitude pixels; and
producing a plurality of component subregion descriptors for each subregion of a pixel region about said pixel amplitude extrema in said plurality of difference images produced from said image.
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Abstract
A method and apparatus for identifying scale invariant features in an image and a further method and apparatus for using such scale invariant features to locate an object in an image are disclosed. The method and apparatus for identifying scale invariant features may involve the use of a processor circuit for producing a plurality of component subregion descriptors for each subregion of a pixel region about pixel amplitude extrema in a plurality of difference images produced from the image. This may involve producing a plurality of difference images by blurring an initial image to produce a blurred image and by subtracting the blurred image from the initial image to produce the difference image. For each difference image, pixel amplitude extrema are located and a corresponding pixel region is defined about each pixel amplitude extremum. Each pixel region is divided into subregions and a plurality of component subregion descriptors are produced for each subregion. These component subregion descriptors are correlated with component subregion descriptors of an image under consideration and an object is indicated as being detected when a sufficient number of component subregion descriptors (scale invariant features) define an aggregate correlation exceeding a threshold correlation with component subregion descriptors (scale invariant features) associated with the object.
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Citations
20 Claims
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1. A method of identifying scale invariant features in an image defined by a plurality of pixels, the method comprising:
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locating pixel amplitude extrema in a plurality of difference images produced from said image by;
comparing the amplitude of each pixel in an image under consideration with the amplitudes of pixels in an area about said each pixel in said image under consideration to identify local maximal and minimal amplitude pixels;
comparing the amplitudes of said local maximal and minimal amplitude pixels with the amplitudes of pixels in a predecessor image to the image under consideration to identify possible maximal and minimal amplitude pixels and comparing the amplitudes of said possible maximal and minimal amplitude pixels with the amplitudes of pixels in a successor image to the image under consideration to identify actual maximal and minimal amplitude pixels; and
producing a plurality of component subregion descriptors for each subregion of a pixel region about said pixel amplitude extrema in said plurality of difference images produced from said image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 20)
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10. An apparatus for identifying scale invariant features in an image defined by a plurality of pixels, the apparatus comprising a processor circuit configured to:
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locate said pixel amplitude extrema in difference images by;
comparing the amplitude of each pixel in an image under consideration, with the amplitudes of pixels in an area about said each pixel in said image under consideration to identify local maximal and minimal amplitude pixels;
comparing the amplitudes of said local maximal and minimal amplitude pixels with the amplitudes of pixels in a predecessor image to the image under consideration to identify possible maximal and minimal amplitude pixels;
comparing the amplitudes of said possible maximal and minimal amplitude pixels with the amplitudes of pixels in a successor image to the image under consideration to identify actual maximal and minimal amplitude pixels; and
produce a plurality of component subregion descriptors for each subregion of a pixel region about pixel amplitude extrema in said plurality of difference images. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. An apparatus for identifying scale invariant features in an image defined by a plurality of pixels, the apparatus comprising:
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means for locating pixel amplitude extrema in a plurality of difference images produced from said image, said means for locating comprising;
means for comparing the amplitude of each pixel in an image under consideration, with the amplitudes of pixels in an area about said each pixel in said image under consideration to identify local maximal and minimal amplitude pixels;
means for comparing the amplitudes of said local maximal and minimal amplitude pixels with the amplitudes of pixels in a predecessor image to the image under consideration to identify possible maximal and minimal amplitude pixels and means for comparing the amplitudes of said possible maximal and minimal amplitude pixels with the amplitudes of pixels in a successor image to the image under consideration to identify actual maximal and minimal amplitude pixels; and
means for producing a plurality of component subregion descriptors for each subregion of a pixel region about said pixel amplitude extrema in said plurality of difference images.
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Specification